<!DOCTYPE html>
<title>CSS Anchor Positioning: Transition when the result of anchor()/anchor-size() changes</title>
<link rel="help" href="https://drafts4.csswg.org/css-anchor-position-1/">
<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/9598">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  .cb {
    display: inline-block;
    position: relative;
    width: 250px;
    height: 250px;
    border: 1px solid black;
  }
  .anchor {
    position: absolute;
    width: 50px;
    height: 40px;
    left: 60px;
    top: 40px;
    background: coral;
    anchor-name: --a;
  }
  .shift {
    left: 80px;
  }
  .grow {
    width: 70px;
  }
  .anchored {
    position: absolute;
    width: anchor-size(width);
    height: 40px;
    position-anchor: --a;
    top: anchor(bottom);
    left: anchor(right);
    transition-duration: 1000s;
    transition-timing-function: steps(2, start);
    background-color: skyblue;
  }
</style>

<div id=anchor_test class=cb>
  <div class=anchor></div>
  <div class=anchored style="transition-property:left"></div>
</div>
<script>
  test(() => {
    let anchor = anchor_test.querySelector('.anchor');
    let anchored = anchor_test.querySelector('.anchored');
    assert_equals(anchored.offsetLeft, 110);
    anchor.classList.add('shift');
    assert_equals(anchored.offsetLeft, 120);
  }, 'Transition when the result of anchor() changes');
</script>

<div id=anchor_size_test class=cb>
  <div class=anchor></div>
  <div class=anchored style="transition-property:width"></div>
</div>
<script>
  test(() => {
    let anchor = anchor_size_test.querySelector('.anchor');
    let anchored = anchor_size_test.querySelector('.anchored');
    assert_equals(anchored.offsetWidth, 50);
    anchor.classList.add('grow');
    assert_equals(anchored.offsetWidth, 60);
  }, 'Transition when the result of anchor-size() changes');
</script>
